An LTE (Long Term Evolution) of which the specifications are designed in 3GPP (3rd Generation Partnership Project), which is a project aiming to standardize a cellular communication technology, supports a cellular/WLAN radio interworking technology in Release 12 and later (see Non Patent Document 1 and 2).
Further, in order to enhance the cellular/WLAN radio interworking technology, a technology is proposed by which data of user terminal is transmitted and received by using both the cellular communication and the WLAN communication (hereinafter, referred to as “cellular/WLAN aggregation”) (see Non Patent Document 3).